/*
** Customized version of nweb23.c modified specifically for serving this
** project's documentation.  The specific MIME types needed for this
** project are the only MIME types permitted and URLs pointing at directoires
** get "index.html" added.
*/
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#define VERSION   23
#define BUFSIZE   8096
#define ERROR     42
#define LOG       44
#define FORBIDDEN 403
#define NOTFOUND  404

struct
{
    char *ext;
    char *filetype;
} extensions [] =
{
    {"html", "text/html"                          },
    {"js",   "application/javascript"             },
    {"json", "application/json"                   },
    {"xml",  "application/xml"                    },
    {"gz",   "application/gzip"                   },
    {"woff2","font/woff2"                         },
    {"ttf",  "font/ttf"                           },
    {"eot",  "application/vnd.ms-fontobject"      },
    {"woff", "font/woff"                          },
    {"svg",  "image/svg+xml"                      },
    {"png",  "image/png"                          },
    {"webmanifest", "application/manifest+json"   },
    {"jpg",  "image/jpeg"                         },
    {"ico",  "image/x-icon"                       },
    {"css",  "text/css"                           },
    {"log",  "text/plain"                         },
    {0,0}
};

bool is_dir(const char *path)
{
    struct stat s;
    return stat(path, &s) == 0 && S_ISDIR(s.st_mode);
}

void logger(int type, char *s1, char *s2, int socket_fd)
{
    int fd, rv;
    char logbuffer[BUFSIZE*2];

    switch (type)
    {
    case ERROR:
        rv = sprintf(logbuffer,"ERROR: %s:%s Errno=%d exiting pid=%d",s1, s2, errno,getpid());
        break;
    case FORBIDDEN:
        rv = write(socket_fd, "HTTP/1.1 403 Forbidden\n"
                   "Content-Length: 185\n"
                   "Connection: close\n"
                   "Content-Type: text/html\n\n"
                   "<html><head>\n"
                   "<title>403 Forbidden</title>\n"
                   "</head><body>\n"
                   "<h1>Forbidden</h1>\n"
                   "The requested URL, file type or operation is not allowed on this simple static file webserver.\n"
                   "</body></html>\n",271);
        rv = sprintf(logbuffer,"FORBIDDEN: %s:%s",s1, s2);
        break;
    case NOTFOUND:
        rv = write(socket_fd, "HTTP/1.1 404 Not Found\n"
                   "Content-Length: 136\n"
                   "Connection: close\n"
                   "Content-Type: text/html\n\n"
                   "<html><head>\n"
                   "<title>404 Not Found</title>\n"
                   "</head><body>\n"
                   "<h1>Not Found</h1>\n"
                   "The requested URL was not found on this server.\n"
                   "</body></html>\n",224);
        rv = sprintf(logbuffer,"NOT FOUND: %s:%s",s1, s2);
        break;
    case LOG:
        rv = sprintf(logbuffer," INFO: %s:%s:%d",s1, s2,socket_fd);
        break;
    }
    /* No checks here, nothing can be done with a failure anyway */
    if((fd = open("nweb.log", O_CREAT| O_WRONLY | O_APPEND,0644)) >= 0)
    {
        rv = write(fd,logbuffer,strlen(logbuffer));
        rv = write(fd,"\n",1);
        rv = close(fd);
    }
    ((void)(rv));
    if(type == ERROR || type == NOTFOUND || type == FORBIDDEN) exit(3);
}

/* this is a child web server process, so we can exit on errors */
void web(int fd, int hit)
{
    int j, file_fd, buflen, rv;
    long i, ret, len;
    char * fstr;
    static char buffer[BUFSIZE+1]; /* static so zero filled */

    ret =read(fd,buffer,BUFSIZE); 	/* read Web request in one go */
    if(ret == 0 || ret == -1)  	/* read failure stop now */
    {
        logger(FORBIDDEN,"failed to read browser request","",fd);
    }
    if(ret > 0 && ret < BUFSIZE)	/* return code is valid chars */
        buffer[ret]=0;		/* terminate the buffer */
    else buffer[0]=0;
    for(i=0; i<ret; i++)	/* remove CF and LF characters */
        if(buffer[i] == '\r' || buffer[i] == '\n')
            buffer[i]='*';
    logger(LOG,"request",buffer,hit);
    if( strncmp(buffer,"GET ",4) && strncmp(buffer,"get ",4) )
    {
        logger(FORBIDDEN,"Only simple GET operation supported",buffer,fd);
    }
    for(i=4; i<BUFSIZE; i++) /* null terminate after the second space to ignore extra stuff */
    {
        if(buffer[i] == ' ')   /* string is "GET URL " +lots of other stuff */
        {
            buffer[i] = 0;
            break;
        }
    }
    for(j=0; j<i-1; j++) 	/* check for illegal parent directory use .. */
        if(buffer[j] == '.' && buffer[j+1] == '.')
        {
            logger(FORBIDDEN,"Parent directory (..) path names not supported",buffer,fd);
        }
    if( !strncmp(&buffer[0],"GET /\0",6) || !strncmp(&buffer[0],"get /\0",6) ) /* convert no filename to index file */
        rv = (long long)(void*)strcpy(buffer,"GET /index.html");
    else if( is_dir(&buffer[5]))
        rv = (long long)(void*)strcat(buffer, "/index.html");

    /* work out the file type and check we support it */
    buflen=strlen(buffer);
    fstr = (char *)0;
    for(i=0; extensions[i].ext != 0; i++)
    {
        len = strlen(extensions[i].ext);
        if( !strncmp(&buffer[buflen-len], extensions[i].ext, len))
        {
            fstr =extensions[i].filetype;
            break;
        }
    }
    if(fstr == 0) logger(FORBIDDEN,"file extension type not supported",buffer,fd);

    if(( file_fd = open(&buffer[5],O_RDONLY)) == -1)    /* open the file for reading */
    {
        logger(NOTFOUND, "failed to open file",&buffer[5],fd);
    }
    logger(LOG,"SEND",&buffer[5],hit);
    len = (long)lseek(file_fd, (off_t)0, SEEK_END); /* lseek to the file end to find the length */
    rv = lseek(file_fd, (off_t)0, SEEK_SET); /* lseek back to the file start ready for reading */
    rv = sprintf(buffer,"HTTP/1.1 200 OK\nServer: nweb/%d.0\nContent-Length: %ld\nConnection: close\nContent-Type: %s\n\n", VERSION, len, fstr); /* Header + a blank line */
    logger(LOG,"Header",buffer,hit);
    rv = write(fd,buffer,strlen(buffer));

    /* send file in 8KB block - last block may be smaller */
    while (	(ret = read(file_fd, buffer, BUFSIZE)) > 0 )
    {
        rv = write(fd,buffer,ret);
    }
    sleep(1);	/* allow socket to drain before signalling the socket is closed */
    close(fd);
    ((void)(rv));
    exit(1);
}

int main(int argc, char **argv)
{
    int i, port, pid, listenfd, socketfd, hit;
    socklen_t length;
    static struct sockaddr_in cli_addr; /* static = initialised to zeros */
    static struct sockaddr_in serv_addr; /* static = initialised to zeros */

    if( argc < 3  || argc > 3 || !strcmp(argv[1], "-?") )
    {
        (void)printf("hint: nweb Port-Number Top-Directory\t\tversion %d\n\n"
                     "\tnweb is a small and very safe mini web server\n"
                     "\tnweb only servers out file/web pages with extensions named below\n"
                     "\t and only from the named directory or its sub-directories.\n"
                     "\tThere is no fancy features = safe and secure.\n\n"
                     "\tExample: nweb 8181 /home/nwebdir &\n\n"
                     "\tOnly Supports:", VERSION);
        for(i=0; extensions[i].ext != 0; i++)
            (void)printf(" %s",extensions[i].ext);

        (void)printf("\n\tNot Supported: URLs including \"..\", Java, CGI\n"
                     "\tNot Supported: directories / /etc /bin /lib /tmp /usr /dev /sbin \n"
                     "\tNo warranty given or implied\n\tNigel Griffiths nag@uk.ibm.com\n"  );
        exit(0);
    }
    if( !strncmp(argv[2],"/",2 ) || !strncmp(argv[2],"/etc", 5 ) ||
            !strncmp(argv[2],"/bin",5 ) || !strncmp(argv[2],"/lib", 5 ) ||
            !strncmp(argv[2],"/tmp",5 ) || !strncmp(argv[2],"/usr", 5 ) ||
            !strncmp(argv[2],"/dev",5 ) || !strncmp(argv[2],"/sbin",6) )
    {
        (void)printf("ERROR: Bad top directory %s, see nweb -?\n",argv[2]);
        exit(3);
    }
    if(chdir(argv[2]) == -1)
    {
        (void)printf("ERROR: Can't Change to directory %s\n",argv[2]);
        exit(4);
    }
    /* Become deamon + unstopable and no zombies children (= no wait()) */
    if(fork() != 0)
        return 0; /* parent returns OK to shell */
    (void)signal(SIGCHLD, SIG_IGN); /* ignore child death */
    (void)signal(SIGHUP, SIG_IGN); /* ignore terminal hangups */
    for(i=0; i<32; i++)
        (void)close(i);		/* close open files */
    (void)setpgrp();		/* break away from process group */
    logger(LOG,"nweb starting",argv[1],getpid());
    /* setup the network socket */
    if((listenfd = socket(AF_INET, SOCK_STREAM,0)) <0)
        logger(ERROR, "system call","socket",0);
    port = atoi(argv[1]);
    if(port < 0 || port >60000)
        logger(ERROR,"Invalid port number (try 1->60000)",argv[1],0);
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    serv_addr.sin_port = htons(port);
    if(bind(listenfd, (struct sockaddr *)&serv_addr,sizeof(serv_addr)) <0)
        logger(ERROR,"system call","bind",0);
    if( listen(listenfd,64) <0)
        logger(ERROR,"system call","listen",0);
    for(hit=1; ; hit++)
    {
        length = sizeof(cli_addr);
        if((socketfd = accept(listenfd, (struct sockaddr *)&cli_addr, &length)) < 0)
            logger(ERROR,"system call","accept",0);
        if((pid = fork()) < 0)
        {
            logger(ERROR,"system call","fork",0);
        }
        else
        {
            if(pid == 0)   	/* child */
            {
                (void)close(listenfd);
                web(socketfd,hit); /* never returns */
            }
            else   	/* parent */
            {
                (void)close(socketfd);
            }
        }
    }
}
